Application of Coffee Silverskin Extract in Biofilms for Scarlet Eggplant Preservation

Coffee processing generates large amounts of agro-industrial residues, including coffee silverskin, a roasting by-product rich in dietary fiber, proteins, minerals, and bioactive compounds with antioxidant potential. Scarlet eggplant (Solanum gilo), widely consumed in Brazil, has high perishability, causing rapid postharvest deterioration and reduced commercial value. Edible films represent a sustainable alternative for extending shelf life by reducing moisture loss and gas exchange while enabling the incorporation of bioactive compounds. This study evaluated cassava starch-based edible films enriched with aqueous coffee silverskin extract for scarlet eggplant preservation. Fruits were subjected to four treatments: control (water), F1 (cassava starch + calcium chloride), F2 (10 mL coffee silverskin extract + calcium chloride), and F3 (cassava starch + 10 mL coffee silverskin extract + calcium chloride). The experiment consisted of 4 treatments with 3 repetitions and each experimental unit 3 fruits, evaluated after 0 and 96 h of storage. Analyses included pH, titratable acidity, soluble solids, and weight loss. Data were analyzed by analysis of variance (ANOVA), followed by Tukey’s test at 5% probability. The aqueous extract presented pH 5.73, titratable acidity of 1.17%, soluble solids of 2.03 °Brix, total phenolic content of 35.04 ± 0.16 mg GAE 100 g⁻¹, and antioxidant activity of 18.75% by DPPH assay. After 96 h, F3 showed lower acidity changes, and all film treatments reduced weight loss compared with the control fruits. These results demonstrate that coffee silverskin extract-enriched edible films are sustainable alternatives for improving scarlet eggplant preservation and valorizing coffee residues through circular economy practices.